Assembly of electrical circuits is often accomplished by mounting a myriad of components on a printed circuit board which is patterned to provide the desired electrical connections between components. Such printed circuit boards, which may be rigid or flexible and are fabricated from a variety of materials, may have the electrical interconnections patterned on one or two sides or may have the interconnections formed on a plurality of planar surfaces which are laminated together to form the printed circuit board.
Accordingly, for purposes of this application, the term printed circuit board is intended to encompass any surface which is patterned to provide electrical interconnections between components. Along with the desired interconnections, the printed circuit board also includes a conductive "footprint" or pattern for receiving each electrical component. A printed circuit board may be designed to receive a variety of circuit component types. Each type differs from the other in the structure used for interconnection to the printed circuit board. In one type of component commonly referred to as a through-hole or feed-through component, connection to the printed circuit board is accomplished by feeding wire leads through holes which extend completely through the printed circuit board. Hence, the term "through-hole" is used as a descriptor for these components. In another type of component, known as surface mount, the body of the component is formed with areas of solder or some other meltable and electrically conductive material. Connection between each of these components and the printed circuit board is achieved by melting this conductive material when it is in contact with appropriately-sized conductive areas on the printed circuit board. Such melting is typically provided by reflowing a solder paste or melting the conductive material and generally adding additional conductive material with a solder wave. In lieu of melting, some surface mount components are produced with a conductive adhesive and, therefore, do not require melting for connection to the printed circuit board.
While through-hole and surface mount technologies are well established, problems do arise in manufacturing when one of the component types required for an assembled printed circuit board is temporarily unavailable. Moreover, the required component value is oftentimes available in the other component type and could be used but for the difference in physical structure used for interconnection. This component shortage can, at times, lead to a shut-down of a particular product line, and redesign of the printed circuit board to accommodate mounting of the available component type is both time-consuming and expensive. Redesign of the printed circuit board, of course, is often not an option for cost reasons, especially when only a small number of the printed circuit boards are to be assembled. Therefore, the result is a shut-down of the product line. Accordingly, it would be extremely desirable if the problems associated with component shortages could be resolved.